This invention relates to air diffusers which are useful in air conditioning and air circulating systems and, more particularly, to ceiling air diffusers providing variable cooling of a room by altering the flow of air to the room.
Typically, air diffusers for supplying conditioned air (primary air) to a room provide for delivery of the primary air in a pattern substantially horizontally and radially outward along the ceiling of the room. This pattern of flow serves to distribute the air from the diffuser throughout the room rather than to allow the primary air to fall directly downward from the diffuser. Occupants of the room who happen to be immediately below the diffuser may experience discomfort or drafts if the diffuser does not mix the primary air with the room air or if the diffuser does not distribute the primary air sufficiently.
As influences upon the room change, it is desirable to alter the flow of primary air to the room to maintain the comfort of occupants of the room. For example, if sunlight no longer enters the room, the amount of primary air should be decreased accordingly. Typically, for larger buildings, the speed of a central fan is controlled so as to reduce the flow of primary air and conserve fan horsepower when cooling requirements are decreased. For smaller buildings with less elaborate cooling systems, the central fan typically operates at a single speed and a separate bypass duct with a modulating damper is used. However, with such less elaborate cooling systems, there is a need for a more economical apparatus to vary the flow of primary air to a room without requiring a separate bypass duct and modulating damper.
It is, therefore, an object of the present invention to provide an air diffuser to economically vary the flow of cooling air to a room without the need to control the speed of a central cooling fan and without requiring a separate bypass duct and modulating damper.
Another problem with existing air diffusers is inadequate mixing of primary air and room air. Although a mixing of the room air with the primary air is often accomplished to some degree by standard diffuser designs, a more thorough mixing of air is desirable. Such thorough mixing provides greater comfort to occupants of the room and allows more economical temperature conditioning by the use of primary air of a lower temperature, thereby reducing the quantity of primary air required vis-a-vis diffusers providing less thorough mixing of primary air and secondary air.
Various alternatives have been proposed to accomplish a more thorough mixing of the pimary air and room air. For example, fan powered induction boxes have been installed in the primary air ducting within a plenum above a false ceiling of a room. Such induction boxes employ a fan to induce the flow of recirculated air (secondary air) from the room through the plenum into an induction box for mixing with the primary air prior to delivery of the primary air to an air diffuser. However, the additional cost of providing the separate structure of the induction box and the added fan and energy requirements make such systems impractical for many applications.
Another approach to providing more thorough mixing of primary air and room air is that of applicant's U.S. Pat. No. 4,181,253, which discloses an air diffuser providing induction of room air directly from a room to the diffuser, without drawing the secondary air through a plenum to a separate induction box. Although such an air diffuser eliminates the expense of a powered induction box and provides sufficient recirculation of room air for some applications, there is a need in other applications for an apparatus providing efficient recirculation of secondary air from more remote areas of the room.
An air diffuser proposed to provide less localized recirculation of room air is disclosed in U.S. Pat. No. 3,732,799 to Spoormaker. The air diffuser proposed therein employs a flared skirt with apertures to admit induced secondary air from a plenum above a false ceiling and a flared divider member movable in parallel relation to the skirt for regulating the flow of induced secondary air. Although the plenum facilitates recirculation of secondary air from remote areas of the room, the air diffuser proposed therein provides no mixing of the primary air and the secondary air until after the primary air and the secondary air are discharged from the air diffuser into the room.
It is, therefore, a further object of the present invention to provide an air diffuser ensuring recirculation of air from remote areas of a room, utilizing the plenum for recirculation of the room air, and providing improved mixing of the secondary air with the primary air prior to discharging the primary air and the secondary air into the room.